module Native

// Disables warn:1204 raised by use of LanguagePrimitives.ErrorStrings.*
#nowarn "1204"

open Fable.Core
open Fable.Core.PyInterop

[<Import("FSharpCons", ".array_")>]
[<AllowNullLiteral>]
type Cons<'T>() =
    [<Emit("$0.allocate($1)")>]
    member _.Allocate(len: int) = nativeOnly


module Helpers =
    let arrayFrom (xs: 'T seq) : 'T[] = Array.ofSeq xs

    let allocateArray (len: int) : 'T[] =
        Array.create len Unchecked.defaultof<'T>

    [<Emit("[x for i, x in enumerate(list($0)+[0]*($1-len($0))) if i < $1]")>]
    let allocateArrayFrom (xs: 'T[]) (len: int) : 'T[] = nativeOnly

    let allocateArrayFromCons (cons: Cons<'T>) (len: int) : 'T[] =
        if isNull cons then
            Cons().Allocate(len)
        else
            cons.Allocate(len)

    //let inline isDynamicArrayImpl arr = Py.Array.isArray arr

    [<Emit("$0+$1")>]
    let concatImpl (array1: 'T[]) (arrays: 'T[] seq) : 'T[] = nativeOnly

    let fillImpl (array: 'T[]) (value: 'T) (start: int) (count: int) : 'T[] =
        for i = 0 to count - 1 do
            array.[i + start] <- value

        array

    [<Emit("functools.reduce($0, $2, $1)")>]
    let foldImpl (folder: 'State -> 'T -> 'State) (state: 'State) (array: 'T[]) : 'State = nativeOnly

    let inline foldIndexedImpl (folder: 'State -> 'T -> int -> 'State) (state: 'State) (array: 'T[]) : 'State =
        !! array?reduce (System.Func<'State, 'T, int, 'State>(folder), state)

    [<Emit("functools.reduce($0, $2[::-1], $1)")>]
    let foldBackImpl (folder: 'State -> 'T -> 'State) (state: 'State) (array: 'T[]) : 'State = nativeOnly

    let inline foldBackIndexedImpl (folder: 'State -> 'T -> int -> 'State) (state: 'State) (array: 'T[]) : 'State =
        !! array?reduceRight (System.Func<'State, 'T, int, 'State>(folder), state)

    // Typed arrays not supported, only dynamic ones do
    let inline pushImpl (array: 'T[]) (item: 'T) : int = !! array?append (item)

    // Typed arrays not supported, only dynamic ones do
    let inline insertImpl (array: 'T[]) (index: int) (item: 'T) : 'T[] =
        !!array?insert(index, item)
        array

    // Typed arrays not supported, only dynamic ones do
    let spliceImpl (array: 'T[]) (start: int) (deleteCount: int) : 'T[] =
        for _ = 1 to deleteCount do
            !!array?pop(start)

        array

    [<Emit("$0[::-1]")>]
    let reverseImpl (array: 'T[]) : 'T[] = nativeOnly

    [<Emit("$0[:]")>]
    let copyImpl (array: 'T[]) : 'T[] = nativeOnly

    [<Emit("$0[$1:]")>]
    let skipImpl (array: 'T[]) (count: int) : 'T[] = nativeOnly

    [<Emit("$0[$1:$1+$2]")>]
    let subArrayImpl (array: 'T[]) (start: int) (count: int) : 'T[] = nativeOnly

    let indexOfImpl (array: 'T[]) (item: 'T) (start: int) : int =
        try
            !!array?index(item, start)
        with ex ->
            -1

    [<Emit("next((x for x in $1 if ($0)(x)), None)")>]
    let findImpl (predicate: 'T -> bool) (array: 'T[]) : 'T option = nativeOnly

    [<Emit("next((i for i, x in enumerate($1) if ($0)(x)), -1)")>]
    let findIndexImpl (predicate: 'T -> bool) (array: 'T[]) : int = nativeOnly

    let inline collectImpl (mapping: 'T -> 'U[]) (array: 'T[]) : 'U[] = !! array?flatMap (mapping)

    let inline containsImpl (predicate: 'T -> bool) (array: 'T[]) : bool = !! array?filter (predicate)

    let inline existsImpl (predicate: 'T -> bool) (array: 'T[]) : bool = !! array?some (predicate)

    [<Emit("all([$0(x) for x in $1])")>]
    let forAllImpl (predicate: 'T -> bool) (array: 'T[]) : bool = nativeOnly

    [<ImportAll("builtins")>]
    [<Emit("list(builtins.filter($1, $2))")>]
    let filterImpl (predicate: 'T -> bool) (array: 'T[]) : 'T[] = nativeOnly

    [<Emit("functools.reduce($0, $1)")>]
    let reduceImpl (reduction: 'T -> 'T -> 'T) (array: 'T[]) : 'T = nativeOnly

    [<Emit("functools.reduce($0, $1[::-1])")>]
    let inline reduceBackImpl (reduction: 'T -> 'T -> 'T) (array: 'T[]) : 'T = nativeOnly

    // Inlining in combination with dynamic application may cause problems with uncurrying
    // Using Emit keeps the argument signature.
    [<Emit("$1.sort(key=functools.cmp_to_key($0))")>]
    let sortInPlaceWithImpl (comparer: 'T -> 'T -> int) (array: 'T[]) : unit = nativeOnly

    [<Emit("sorted($1, key=functools.cmp_to_key($0))")>]
    let sortWithImpl (comparer: 'T -> 'T -> int) (array: 'T[]) : 'T[] = nativeOnly

    [<Emit("$1.sort(key=functools.cmp_to_key($0))")>]

    let copyToTypedArray (src: 'T[]) (srci: int) (trg: 'T[]) (trgi: int) (cnt: int) : unit =
        let diff = trgi - srci

        for i = srci to srci + cnt - 1 do
            trg.[i + diff] <- src.[i]
